最近一个项目要用到.Net，用久了Hibernate直接用ADO.NET手写SQL的话真还有点不适应，还好NHibernate提供了对.Net的ORM支持。在使用Hibernate的时候

，可以使用ThreadLoca来存放Session的。ThreadLoca是给每个线程提供单独的静态变量，在一个线程内部共享，而不同的线程间不共享。在.Net中找了好长时间

，终于找到了ThreadStaticAttribute ，它指示静态字段的值对于每个线程都是唯一的。在WinFrom,控制台应用程序和类库等中的确是可以用的。但在Asp.Net中

HttpRequest则可能有多个线程为其服务。如果用ThreadStaticAttribute 的话，很有可能同一个请求使用多个线程那么数据就不能共享了。不过我们可以使用

HttpContext.Current.Items来存放session。所以就自己写一个等同ThreadLocal的类来存放Session,代码如下：

    /// <summary>
    /// 在.NET应用程序中,为一个单线程
    /// 在ASP.NET应用程序中,为一个请求
    /// </summary>
    /// <author>Kevin</author>
    public class SessionHolder
    {
        private HolderSupport holderSupport;

        public SessionHolder()
        {
            if (HttpContext.Current != null)
            {
                holderSupport = new AspNetHolderSupport();
            }
            else
            {
                holderSupport = new NetHolderSupport();
            }
        }

        public ISession Get()
        {
            return holderSupport.Get();
        }

        public void Set(ISession session)
        {
            holderSupport.Set(session);
        }

        class NetHolderSupport : HolderSupport
        {
            [ThreadStatic]
            private static ISession threadLocal;

            public ISession Get()
            {
                if (threadLocal != null)
                {
                    if (!threadLocal.IsConnected)
                    {
                        threadLocal.Reconnect();
                    }
                }

                return threadLocal;
            }

            public void Set(ISession session)
            {
                if (session == null)
                {
                    threadLocal = null;
                    return;
                }

                if (!session.IsConnected)
                {
                    session.Reconnect();
                }

                threadLocal = session;
            }
        }

        class AspNetHolderSupport:HolderSupport
        {
            private readonly object DEFAULT_SESSION_KEY = new object();

            public ISession Get()
            {
                return HttpContext.Current.Items[DEFAULT_SESSION_KEY] as ISession;
            }

            public void Set(ISession session)
            {
                if (session != null)
                {
                    HttpContext.Current.Items.Add(DEFAULT_SESSION_KEY, session);
                }
                else
                {
                    HttpContext.Current.Items.Remove(DEFAULT_SESSION_KEY);
                }
            }
        }

        interface HolderSupport
        {
            ISession Get();
            void Set(ISession session);
        }
    }

 

    自己又写了一个SessionFactoryUtil类，用来打开和关闭Session,代码如下：
   

public abstract class SessionFactoryUtil
    {
        private static readonly object lockObj = new object();
 
        private static ISessionFactory factory;

        private static readonly SessionHolder holder = new SessionHolder(); 

        public static ISessionFactory Factory
        {
            get
            {
                if (factory == null)
                {
                    lock (lockObj)
                    {
                        if (factory == null)
                        {
                            Configuration cfg = new Configuration();
                            cfg.AddAssembly(Assembly.GetExecutingAssembly());
                            factory = cfg.BuildSessionFactory();
                        }
                    }
                }

                return factory;
            }
        }

        public static ISession CurrentSession()
        {
            ISession session = holder.Get();

            if (session == null)
            {
                session = Factory.OpenSession();
                holder.Set(session);
            }

            return session;
        }

        public static void CloseSession()
        {
            ISession session = holder.Get();

            if (session != null)
            {
                session.Close();                
            }

            holder.Set(null);
        }
    }